In transmissions whose shift cylinders, comprising shift actuators for carrying out shift operations, are actuated by a hydraulic control system, it can be the case that because of design considerations the actuators, i.e. the shift cylinders, cannot be integrated directly in the hydraulic control unit. In such a case it is advantageous if no other component is present between the housing in which the actuator is arranged and the hydraulic control unit, since tolerances are disadvantageously increased if a further component is present.
The hydraulic control unit must be fitted without leaks at the transfer points but since they should not be stressed due to the risk that sliding components may stick, the interface between the control unit and the actuator housing should be defined by a machined surface.
If there is any intermediate component between the control unit and the actuator housing, the interfaces must be sealed with elastic seals, this however increases costs and the elastic seals have the drawback of not being as reliable as direct-contact, planar sealing surfaces.